1. Field of the Invention
The present invention relates to a converter with a damping mechanism for preventing resonances, having a rectifier, an inverter and an intermediate circuit which connect the rectifier with the inverter, and having two conductors connected to different potentials.
2. Discussion of Related Art
Such converters are used for providing electrical drive mechanisms with energy.
Today, hardly any technological field can get along without modem, electronically commutated drive mechanisms. Therefore a continuous development process is taking place for making such drive mechanisms even more powerful, and in the course of this to make them useful for still further applications. So-called direct drive mechanisms, whose torque is directly transferred without a transmission to the desired application, for example, become generally accepted in more and more fields. Such direct drive mechanisms are already available for very high torques or, in the form of linear drive mechanisms, for very high forces.
Parasitic capacitances in the drive mechanism play an increasingly greater role as a result of the construction of such direct drive mechanisms, such as described in EP 0 793 870 B1, which corresponds to U.S. Pat. Nos. 5,642,013 and 5,910,691, the entire contents of each of which is incorporated herein by reference. In connection with a converter for supplying the drive mechanism with energy, systems capable of oscillations with relatively low resonance frequencies in the range of some 10 kHz are created.
Converters operating in accordance with the principle of the step-up converter in particular generate undesired excitations of these resonance frequencies because of system-related jumps in the voltage of the intermediate circuit. Thus, observations have already shown that in connection with such converters oscillations occurred at drive mechanisms with particularly high parasitic capacitances, and therefore particularly low resonance frequencies, which led to the destruction of the drive mechanism. In the course of this, voltages of such a size occurred at the neutral point of the drive mechanism that the insulation of the neutral point to ground was punctured by the partial discharge.
Several attempts have already become known for avoiding such problems. They have in common that the undesired resonance oscillations are damped. This is either performed directly at the drive mechanism or in the converter.
An example for the first mentioned attempt is provided by DE 100 59 334 A1, which corresponds to U.S. Pat. No. 6,583,598, the entire contents of which are incorporated herein by reference. How flashovers toward ground can be prevented by passive electrical components between the neutral point and ground is described there. However, the disadvantage of such solutions is that the additional electrical components require considerable structural space and can therefore not easily be employed with every application.
A solution within the converter is described in DE 100 64 213 A1, which corresponds to U.S. Patent Application Publication No. US 2002-113585 A1, the entire contents of which are incorporated herein by reference. Starting from the realization that the inductance of the input choke of the converter is an essential component of the oscillatory circuit consisting of converter and drive mechanism, a damping element is proposed, which is integrated into the input choke of the converter and is transformer-coupled.